The Electromechanical Battery (EMB): Flywheel Energy Storage for Vehicular Applications" by Bob Yamamoto and Dick Post of LLNL

• 1. Flywheel Energy Storage for Vehicular ApplicationsLLNL-PRES-645065This work was performed under the auspices of theU.S. Department of Energy by Lawrence LivermoreNational Laboratory under contract DE-AC52-07NA27344.Lawrence Livermore National Security, LLCDick Post and Bob Yamamoto

2. The only present competition in the commercial electricand hybrid-electric area is the electrochemical battery,although EMBs are being used in racing vehicles forpower assist (~200 HP increase for short burst durations). With respect to the cost of an EMB battery pack relative toan electrochemical one, while no detailed analysis hasbeen performed, the simplicity of the proposed systemsand the absence of special fabrication techniques augueswell for competitive cost.LLNL-PRES-645065 Lawrence Livermore National Laboratory2 3. LLNL-PRES-645065 Lawrence Livermore National Laboratory 3 4. LLNL has developed a new generation of modular flywheel storagesystems based on the use of some special technologies, includingpassive magnetic bearings and a novel type of electrostatic generatorthat is very light in weight and, since it has near 100 percent efficiency,does not require active cooling. In these respects these new designs differ greatly from presentcommercially available flywheel storage systems, being especiallysuited to meet the severe requirements of vehicular use. Computer-based simulations predict that the use of the new LLNL-designflywheel modules may allow a doubling of the range of electricautomobiles over that now obtained from the same battery-pack weightof electrochemical batteries, without the attendant problems of limitedcycle life, cell monitoring and cooling, fire hazard, and hazardous-wastedisposal.LLNL-PRES-645065 Lawrence Livermore National Laboratory4LLNL EMB DesignFor Bulk Storage 5. Electrostatic Generator/Motor (ESG):(very high efficiency with near-zero internal heat generation, utilizing anextremely simple and lightweight structure, eliminating point-loadingstress-induced areas).Passive Magnet Bearings:(permanent magnets are used to dynamically stabilize the rotatingflywheel system, eliminating the need for complicated sensors andcontrol circuits, which in turn, eliminates heat generation in the vacuumchamber and the corresponding active cooling system requirement).Carbon Fiber Composite Flywheel rotor employing special mechanicaldesigns:(high-strength, low-density carbon composite material enables increasedkinetic energy storage while achieving significant system weight savings).LLNL-PRES-645065 Lawrence Livermore National Laboratory 5 6. The current state of the development of the new-generationEMBs at LLNL is that it is a work in progress, presently beingdirected toward bulk-storage applications and involving theconstruction of test models of the passive bearing stabilizer,electrostatic generator and electrical charging circuits backedup by computer simulations. Work on vehicular applications of the new-design EMBs hasbeen limited to computer simulations of the mechanical andelectrical components of small modular units, involving thevehicle-related special problems, such as the transientaccelerations that will occur during operation, and the need forlong self-discharge times.LLNL-PRES-645065 Lawrence Livermore National Laboratory6 7. Trump-type charging circuit Parametric-resonance charging circuitVoltage across variable condenser0.0002 0.0004 0.0006 0.0008 0.0010 0.0012Charging dc voltage = 46.9 kVVoltsAC Power output = 1.83 kW @ 40 kHzVoltage across variable condenser0.0002 0.0004 0.0006 0.0008 0.0010 0.0012Charging dc voltage = 24.4 kVVoltsAC Power output = 134 kW @ 40 kHzsec.5000040000300002000010 000sec.5000040000300002000010 000Note: After condenser is charged no power is drawn from charging power supply.LLNL-PRES-645065 Lawrence Livermore National Laboratory 7 8. The new-generation LLNL modular EMBs on-going work involveconcepts that have never before been incorporated in flywheelenergy systems, and these concepts open up new opportunities forapplications such as battery packs for full-electric or hybrid-electricvehicles. The performance indicators that the new EMBs offer thatdifferentiate them from conventional flywheel systems orelectrochemical batteries include simplicity of design, no need forcooling systems, decades-long lifetime with no degradationassociated with number of cycles or depth of discharge, and thepotential to achieve twice the stored energy density (Watt-hrs/kilogram) as that typically obtainable from electrochemicalbattery packs.LLNL-PRES-645065 Lawrence Livermore National Laboratory8 9. Genaro [email protected] Lawrence Livermore National Laboratory 9